package com.yuanxiao.sqlSession;

import com.yuanxiao.pojo.Configuration;
import com.yuanxiao.pojo.MappedStatement;
import com.yuanxiao.utils.GenericTokenParser;
import com.yuanxiao.utils.ParameterMapping;
import com.yuanxiao.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor  implements Executor{
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... parms) throws Exception {
        //注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();
        //获取sql语句         select * from user where id=#{id}# and username=#{username}#
        String sql = mappedStatement.getSql();
        //转换sql语句                select * from user where id=？ and username=？ 转换过程中对 #{}解析出来存储
        BoundSql boundSql=  getBoundSql(sql);
        //获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        //设置参数
            //获取参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramterTypeClass=  getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = paramterTypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(parms[0]);
            preparedStatement.setObject(i+1,o);
        }
        //执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        //封装返回结果集
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);
        ArrayList<Object> objects = new ArrayList<>();
        while (resultSet.next()){
            Object o = resultTypeClass.newInstance();
            //取出resultSet元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <=metaData.getColumnCount() ; i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段值
                Object value = resultSet.getObject(columnName);
                //使用反射或者内省根据数据库表和实体的对应关系，完成结果集封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            objects.add(o);
        }
        return (List<E>) objects;
    }

    @Override
    public void execute(Configuration configuration, MappedStatement mappedStatement, Object... parms) throws Exception {
        //注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();
        //获取sql语句         select * from user where id=#{id}# and username=#{username}#
        String sql = mappedStatement.getSql();
        //转换sql语句                select * from user where id=？ and username=？ 转换过程中对 #{}解析出来存储
        BoundSql boundSql=  getBoundSql(sql);
        //获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        //设置参数
        //获取参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramterTypeClass=  getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = paramterTypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(parms[0]);
            preparedStatement.setObject(i+1,o);
        }
        //执行sql
         preparedStatement.execute();
    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if(paramterType!=null){
           return Class.forName(paramterType);
        }
        return null;
    }

    /**
     * 完成对#{}的解析工作， 将#{}用？代替。并解析出值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类。配合标记解析器来完成对占位符的解析工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        //标记解析器
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
       //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //解析出来的参数
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        return new BoundSql(parseSql, parameterMappings);
    }
}
